Cancer is one of the major causes of death worldwide, and 7.9 million people died from cancer, accounting for 13% of the total deaths in 2007. With the increase in the aging population worldwide, the number of cancer patients is expected to increase. As reported by the World Health Organization, it is estimated that 13 million people will die from cancer in 2030. In recent years, many molecular targeted drugs against specific molecules as therapeutic targets have been developed, some of which have been confirmed to be clinically effective in prolonging the survival time of patients. Examples of such drugs include tyrosine kinase inhibitors such as imatinib, erlotinib, and trastuzumab. Many of such molecular targeted drugs will be effective against cancers that are aberrantly activated by amplification, mutation, and translocation of target genes, overexpression of target proteins, and the like. Conversely, these molecularly targeted drugs presumably cannot treat patients with cancers caused by genes that are not targeted by the drugs, and it is desirable to develop novel pharmaceutical agents for patients for whom existing pharmaceutical agents are not effective.
The Src kinase family is a family of non-receptor tyrosine kinases, and is composed of Src, Fyn, Yes1, Lck, Lyn, Hck, Fgr, and Blk. The Src kinase family interacts with, for example, receptors such as receptor tyrosine kinases and membrane proteins such as integrins, and carries out various signal transductions such as cell proliferation, cell adhesion, and angiogenesis (Non-patent Document 1). The Src kinase family is known to be overexpressed in various types of cancers, and it is known to be associated with cancer malignancy and survival (Non-patent Document 2). For these reasons, it is considered that inhibition of the Src family kinases in cancer tissues can be a promising therapy for various types of cancers, and Src family kinase inhibitors such as dasatinib and bosutinib have been developed. However, existing Src family kinase inhibitors do not show a sufficient effect clinically as Src family kinase inhibitors due to their poor kinase selectivity (Non-patent Document 3). Accordingly, more selective and potent Src family kinase inhibitors are desired.